Conventional bats typically have an axisymmetric stiffness about a swinging axis (i.e., longitudinal axis) and are monolithic structures made from a single material, such as aluminum or wood. The stiffness is defined in a three point bending test with the handle and barrel supported in a fixture and a load applied to a location somewhere in between. By measuring force and deflection, stiffness is calculated. Some bats may be configured as two-piece bats having one stiffness associated with the handle and a different stiffness associated with the barrel, respectively. The term “bat” is used in its broadest sense herein in that a bat may refer to a baseball bat, a softball bat, or any other type of bat that is used for any type of bat-n-ball game.
Some players prefer a lower bat stiffness to produce a faster bat speed with a more pronounced “whip effect.” A lower stiffness bat may also have greater shock dampening to reduce the amount of vibration or “sting” as mainly felt by the player's hands during a collision between the but and the ball. Other players prefer a higher bat stiffness because it may allow the player to have better spatial control, which may correspond to the player being better able to adjust the bat in a vertical plane when swinging. Generally, a vertical position of a pitched ball varies or changes as it approaches the plate, so the player must make quick, often split second, vertical adjustments with the bat to prevent a strike or foul ball.
Most bats intended for amateur play are made from aluminum composites, or both and have a uniform axisymmetric stiffness. Wood bats, on the other hand, have a natural grain which generally provides a different stiffness in different planes normal to the bat's swinging axis. For instance, bats made from Ash wood are typically stronger when hit on an edge grain, so a bat manufacturer will usually place the label at a right angle relative to the edge grain, which in turn indicates to the player to hold the bat with the label facing skyward or up.
Some examples of conventional bats are briefly discussed herein, U.S. Pat. No. 7,086,973 to Wells et al. describes a bat having a non-circular handle with beveled, planar surfaces for accomplishing a favorable hand alignment and feel. The beveled surfaces provide a tactile guide that indicates a certain alignment the player can feel without visually verifying his or her hand position. Further, the '973 patent describes a baseball bat composed entirely of wood, but can also be composed at least in part of a suitable metal or even a composite material so long as the handle does not involve a resilient cushioning member, which isolates the finger tips of the batter from the planar regions of bat handle so that the sensory input provided is significantly diminished and therefore useless for any training purposes.
The following patents are assigned to Jas D. Easton, Inc. and Easton Sports, Inc., respectively, both from Van Nuys, Calif. U.S. Pat. No. 5,593,158 to Filice et al. describes a bat having a flexible connection between the handle and barrel to reduce shock transmitted to the player's hands in the event of an off-center hit. The respective stiffnesses of the handle portion and the barrel portion are uniform and axisymmetric. U.S. Pat. No. 7,572,197 to Chauvin et al. describes a bat having a flexible joint between the handle and barrel, where the may be a non-continuous or non-uniform structural joint. The bat includes some rotationally distinct features such as protruding flanges or radial strips that are arranged uniformly and axisymmetrically. U.S. Pat. No. 7,442,135 to Giannetti et al. describes a one-piece bat having an indented flexural focus region, which may be located in the handle, barrel or a transition section of the bat.
The following patents are assigned to Wilson Sporting Goods Company from Chicago, Ill. U.S. Pat. No. 6,702,698 to Eggiman et al. describes a bat having a stiff transition section with a flexible handle that provides some amount of whip action during the swing and shock attenuation during the hit. Again, the handle, transition section and barrel each have uniform, axisymmetric stiffnesses, respectively. U.S. Pat. No. 7,097,578 to Guenther et al. describes a bat without rotational stiffness differences that employs a round handle making the bat swingable in any orientation.